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+## Copyright (C) 1996, 1998 Auburn University.  All rights reserved.
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by the
+## Free Software Foundation; either version 2, or (at your option) any
+## later version.
+##
+## Octave is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+## for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{n}, @var{nz}, @var{m}, @var{p}, @var{yd}] =} sysdimensions (@var{sys}@{, @var{opt}@})
+## return the number of states, inputs, and/or outputs in the system
+## @var{sys}.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## system data structure
+##
+## @item opt
+## String indicating which dimensions are desired.  Values:
+## @table @code
+## @item "all"
+## (default) return all parameters as specified under Outputs below.
+##
+## @item "cst"
+## return @var{n}= number of continuous states
+##
+## @item "dst"
+## return @var{n}= number of discrete states
+##
+## @item "in"
+## return @var{n}= number of inputs
+##
+## @item "out"
+## return @var{n}= number of outputs
+## @end table
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item  n
+##  number of continuous states (or individual requested dimension as specified
+## by @var{opt}).
+## @item  nz
+##  number of discrete states
+## @item  m
+##  number of system inputs
+## @item  p
+##  number of system outputs
+## @item  yd
+##  binary vector; @var{yd}(@var{ii}) is nonzero if output @var{ii} is
+## discrete.
+## @math{yd(ii) = 0} if output @var{ii} is continous
+## @end table
+## @end deftypefn
+## @seealso{sysgetsignals and sysgettsam}
+
+function [n, nz, m, p, yd] = sysdimensions (sys, opt)
+
+  if(nargout > 5 | nargin < 1 | nargin > 2)
+    usage("[n,nz,m,p[,yd]] = sysdimensions(sys{,opt})");
+  elseif(!is_struct(sys))
+    usage("[n,nz,m,p] = sysdimensions(sys)");
+  elseif(nargin == 1)
+    opt = "all";
+  endif
+
+  n = sys.n;
+  nz = sys.nz;
+  m = length(sysgetsignals(sys,"in"));
+  p = length(sysgetsignals(sys,"out"));
+  yd = sys.yd;
+  valid_options = list("all","cst","dst","st","in","out");
+  valid_values = list(n,n,nz,n+nz,m,p);
+
+  valid_opt = 0;
+  for ii=1:length(valid_options)
+    if(strcmp(nth(valid_options,ii),opt))
+      n = nth(valid_values,ii);
+      valid_opt = 1;
+      if(ii > 1 & nargout > 1)
+        warning("opt=%s, %d output arguments requested",opt,nargout);
+      endif
+    endif
+  endfor
+
+  if (! valid_opt)
+    error ("invalid option passed = %s", opt);
+  endif
+
+endfunction